Coil winding method and apparatus

ABSTRACT

A method and apparatus for winding a coil for an electric machine or the like onto a polygonal former. A wire guide is rotated through a circular path relative to the former on which the coil is being wound; and additional movements are superimposed on said circular path such that the resultant path is flattened, relative to a circle, along at least the longest side of the polygon and /or the angular speed of the former and the wire guide is decreased at least at the angular range where the wire is laid onto said longest side.

i111 3,810,587 [451 May 14, 1974 United States Patent [1 .1

Muskulus COIL WINDING METHOD AN APPARATUS [75] Inventor: Willi Muskulus, Bergen-Enkheim,

Germany [73] Assignee: Blazer Droll KG., Neiderdorfelden,

Germany [22] Filed: Mar. 23, 1972 21 App]. No.: 237,265

[30] Foreign Application Priority Data Mar. 31, 1971 Germany 2115579 [52] US. Cl 242/7.03, 242/7.l l, 242/7.13 [51] Int. Cl. H0lf 41/06 [58] Field of Search 242/7.03, 7.02, 7.13, 7.21, 242/45, 147

[56] References Cited UNITED STATES PATENTS 2,858,992 11/1958 Wentz 242/2 2,657,868 11/1953 Breazeall ..242/45 Primary ExaminerBilly S. Taylor Attorney, Agent, or Firm-Larson, Taylor and Hinds [5 7] ABSTRACT A method and apparatus for winding a coil for an electric machine or the like onto a polygonal former. A wire guide is rotated through a circular path relative to the former on which the coil is being wound; and additional movements are superimposed on said circular path such that the resultant path is flattened, relative to a circle, along at least the longest side of the polygon and /or the angular speed of the former and the wire' guide is decreased at least at the angular range where the wire is laid onto said longest side.

22 Claims, 11 Drawing Figures Pmmrenmmm 3810.587.

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sum 100F10 1 COIL WINDING METHOD AND APPARATUS BACKGROUND OF THE INVENTION The invention relates to a coil winding apparatus for the winding of coils witha polygonal cross-section onto a former, whereby a wire guide rotates on a circular path with reference to the former.

Coils with round cross-sections are now wound with a very high rotary speed, whereby .a wire guide rotates coaxially with reference to the main axis of the coil on a circular path. However, difficulties arise when other than round coils are wound at a high speed. Even if the wire guide rotates in a circular path in this case around the coil former, still the wire will unwind with an uneven speed, which leads to strong accelerating forces. In order that these forces do not reach an impermissible value at which it might be expected that the wire would break, the winding speed, depending on the shape of the coil, must be kept much lower than in the case of winding round coils.

The irregularities during one rotation while winding noncircular coils also cause an imprecise guidance of the wire. In order to ameliorate this disadvantage at least in the individual case, it has been known from German published application No. 1,514,553 to provide a coil former of a deviating cylindrical shape and along which the entire periphery has a finite radius of curvature of a uniform algebraic sign, with a corresponding cylindrical guide on which rollers run, which turn the coil former and align it at all times with reference to the wire guide such that both the winding angle of the wire on the former and the distance between the winding point and the wire guide are kept essentially constant.

However, this known winding process will not allow a high winding speed. Moreover, it basically is not suited to winding coils with a plygonal cross-section. Not only is the wire exposed to particularly strong accelerating forces, but also it strikes violently against the flat sides of the polygonal cross-section, recoils, and at the same time, and also because of the cyclic nonuniform unwinding speed between the wire guide and the coil, vibrates transversely, which prevents one turn of the coil from being placed neatly beside the other. This requirement that the adjacent windings be placed neatly one beside the other, when winding relatively long flat rectangular coils, can be accomplished only at half or one-third the rotary speeds, as compared to winding round coils.

Thus, there exists a need for a new and improved method and apparatus for winding polygonal formers at high speeds.

SUMMARY OF THE INVENTION Thus, it is a purpose of the invention to provide a new and improved method and apparatus for winding coils onto polygonal formers which will permit such winding to be accomplished at high speed.

According to the invention, for the purpose of winding coils with a polygonal cross-section at high speed, the proposal is made to superimpose on the circular main rotary movement a cyclical additional movement, flattening the circular path at least as compared to the longest lateral edges of the former and/or decreasing the relative angular speed between former and wire guide at least in the angular areas in which the wire comes to fit against the longest side of the former.

In the case of such a coil winding apparatus, the extreme tension peaks in the wire are eliminated and the wire will not strike the flat sides of the former as violently. Consequently, in turn, there will be no transverse vibrations of the wire which may now be placed precisely with the predetermined helical pitch onto the former. The winding speed now can amount to a multiple of the winding speed, achievable on winding arrangements with wire guides and coils running circularly.

Thus, it is an object of this invention to provide a new and improved method for winding coils onto polygonal formers.

It is another object of this invention to provide a new and improved apparatus for winding coils onto polygonal formers.

It is another object of this invention to provide a new and improved method and apparatus for winding coils onto polygonal formers which minimizes the large accelerations which occur with circular path wire formers immediately after the wire is laid onto at least the longest side of the polygon.

It is another object of this invention to provide a new and improved method and apparatus for winding coils onto polygonal formers wherein the wire guide rotates through a circular path, onto which path additional movements are superimposed such that the resultant path is flattened, relative to a circle, at least adjacent the longest side of the polygon.

It is another object of this invention to provide a new and improved method and apparatus for Winding a coil onto a polygonal former wherein the angular speed of the wire guide relative to the former is decreased at the point where the wire is laid onto the longest side of the polygonal former.

Other objects and the advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS There follows a detailed description of preferred embodiments of the invention to be read together with the accompanying drawings in which:

FIG. 1 is a schematic representation of the winding process of winding a coil onto a rectangular former by means of a wire guide rotating in a circular path.

FIG. 2 is a graph of the wire unwinding speed and acceleration as a function of the angular speed of the wire guide rotating in the circular path according to FIG. 1.

FIG. 3 is a schematic representation of the path of movement of the wire guide during winding of a coil onto a rectangular former as in FIG. 1 but wherein the resultant path of the wire guide is an ellipse.

FIG. 4 is a graph similar to FIG. 2 but for the winding process of FIG. 3.

FIG. 5 is a schematic representation of the path of movement of the wire guide of a winding arrangement according to the present invention for winding a square coil onto a square former.

FIGS. 6 through 9 are longitudinal sectional views showing four different embodiments of coil winding apparatus, each operating in accordance with the features of the present invention.

FIG 9A is an end elevation view of FIG. 9.

FIG. 10 is a longitudinal sectional view of a coil winding apparatus similar to that shown in FIG. 6 but including two wire guides operating simultaneously.

DETAILED DESCRIPTION OF THE Referring now to the figures, like elements are represented by like numerals throughout the several views.

Before discussing the concrete embodiments described by way of example with reference to FIGS. 6 to 10, it would be helpful to first of all explain their operation as compared to heretofore known coil winding apparatus with circularly running wire guides. Referring generally to FIGS. 1-5, and first of all specifically to FIGS. 1 and 3, in both cases a rectangular elongated former 10 is to be wound. According to FIG. I the wire guide circles around the former 10 in the usual manner. In FIG. 3, on the other hand, the wire guide moves around the former on an elliptically shaped path. In the two drawings several points in the path of travel of the wire guides are given; for FIG. 1 A1, B1, C1, D1, E1, and F l and for FIGS. 3, A2, B2, C2, D2, E2, and F2. Points with corresponding numerical subscripts corre spond to one another and the distance between successive points on each figure represent constant time intervals. In additions, the points SI and T1 in FIG. 1 or S2 and T2, in FIG. 3 have been drawn in as special positions of said wire guide. Whenever the wire guide passes through the points S1 or S2 in the path, the winding wire fits against the shorter side of former l and whenever the wire guide passes through points T, or T the wire fits against the longer side of former 10.

It can readily be seen from a comparison of the lengths of the wire between former and the wire guide in the variously drawn positions A1 to F1 in FIG. I and A2 to F2 in FIG. 3, that the increase in length of the wire between A1 and B1, B1 and C1, C1 and D1, etc., and hence also the change in length per unit of time, as compared with the change in length between positions A2 and B2, B2 and C2, C2 and D2,. etc., according to FIG. 3, is much more irregular. The reason for this is, on the one hand, that because of the shapes of the curvesin the one case a circle, in the other an ellipse and even with a uniform speed along curved paths, the speed component of the wire guide in the direction perpendicular to the longitudinal axis of former 10 is much larger at T1 in the circular path than at point T2 of the elliptical path. Whereas for example the unwinding speed of the wire just before. point T1 approaches zero, it will be approximately equal to the path speed of the wire guide immediately after TI, i.e., after the wire is laid against the-long side of former 10. On the other hand, it becomesclear from FIG. 3, that the speed component of the wire guide in the direction perpendicular to the axis of former I0 is still quite considerable at point T2, which means that the wire unwinding speed immediately prior to the wire laying against the long side of the former 10 still has a certain high value, so that the laying of the wire against the long side of the former does not suddenly increase the wire unwinding speed as it does in the case of the circular path according to FIG. 1.

In accordance with the present invention, the technical realization of the advantage of the elliptical path, by means of superimposed circular movements as shown in FIGS. 6 to 10 with respect to several concrete examples, leads to the fact that, in the case of the ellipse according to FIG. 3 and likewise in the case of the approximately square path of movement according to FIG. 5, the tangentially measured path speed is much lower in the more curved ranges of the path than in those flattened ranges opposite to the long sides of former 10. This is illustrated in the various path distances A2-B2, B2-C2, C2-D2, etc. In the case of the coil winding apparatus proposed according to the present invention therefore, at path point T2 not only is the speed component in the direction'perpendicular to the axis of former 10 smaller percentagewise than in the case of the circular path, but also the absolute value of the speed is lower in the case of T2 than Tl despite the fact that the revolutions per minute is the same in both cases.

The speed and acceleration conditions of the two winding apparatus, compared in FIGS. 1 and 3, are shown by way of example in FIG. 2 and 4. The diagrams are self-explanatory. What is particularly important in the case of the present invention is that the considerable jump in acceleration at point Tl according to FIG. 2 is decreased. In the case of the elliptical path according to FIG. 4, the jump in acceleration is of course longer at S2 than at point S1 of the circular path but the important thing is that the largest sudden change in acceleration in the elliptical path has been reduced to about one-half to one-fourth of the maximum change in acceleration at point T1 of the circular path. Since the accelerating forces in the case of the path of movement proposed here are so much smaller, it will be possible to wind with a correspondingly higher speed.

FIG. 5 shows how the concept of the present invention can also be applied to the winding of a former with a square cross-section. The subsequently described arrangements according to FIGS. 6 to 10 are suitable both for the production of an elliptically shaped and also triangular, square, pentagonal, or hexagonal paths of movement of the wire guide. Which path will be used is determined according to the r.p.m. ratio of the superimposed speeds and according to the length of the eccentrics. A comparison of FIGS. 3 and 5 shows, of course, that the most unfavorable winding conditions exist in the case of long flat coils. A coil with a hexagonal cross-section would be wound, for the sake fo simplicity, again by means of a circularly rotating wire guide although in this case too the winding with a wire guide guided along an approximately hexagonal path with rounded corners would provide more favorable accelerating conditions.

Moreover, as FIG. 5 shows, it can be effective to turn the path of movement of the wire guide angularly somewhat with reference to the former, so that the sides of the path will not lie parallel to the corresponding sides of the former. As a result of this, points T3 or S3 of the path are shifted to the more favorable area of the path of movement of the wire guide.

A first embodiment of a coil winding apparatus by way of example and according to the invention is shown in FIG. 6. In this case a drive shaft 14 is driven by a suitable rotary drive mechanism (not shown) with a constant rotary speed. At the front end of shaft 14,

the former 10 or 12 is attached firmly to rotate therewith. Shaft 14 is mounted in a housing 20 by means of bearing bushes l6 and 18, in which housing an additional shaft 26 is mounted parallel to shaft 14 in bearing bushes 22 and 24. At its front end, shaft 26 carries a wire guide 28 fixedly to rotate therewith, and eccentrically. The winding wire 30 is guided through the hollow shaft 26 to the guide 28. The inlet and outlet for the wire in shaft 26 are protected by inserts 32 and 34 of a hard material. The same is true for the exit opening of the wire from the wire guide 28, on which likewise a hardened insert 36 has been provided. The deflection of the wire between shaft 27 and wire guide 28 is accomplished via a roll 38 mounted on said wire guide.

Shaft 26 is rotated with wire guide 28 from shaft 14 via toothed pulleys 40 and 42 and a toothed belt 44 connecting the two pulleys. In order to produce an elliptical shaped rotary path of wire guide 28 reference to a flat, elongated former 10, the number of teeth of pulleys 40 and 42 are 2:1. The relative angular positions of shafts l4 and 26 at the same time have been selected such that the wire guide 28 is at the most curved portions of the path when it is in line with the long side of the former. When the former has a triangular or square cross-section, the r.p.m. ratio of shafts l4 and 26 must amount to 1:3 or 1:4.

The feed of the coil is accomplished in FIG. 6 by an axial shift of shaft 14, to which is fixedly connected for rotation therewith toothed pulley 40, by way of a spring in groove 15, making possible said axial shifting. During winding ofa coil, normally several layers of wire are applied to former or 12, for which purpose shaft 14 is shifted back and forth several times.

Referring to FIG. 7, a drive motor (not shown) rotates a shaft 46 which is mounted by means of a bearing bush 48 in a housing 50. A bracket 52 carrying an additional shaft 54 is seated at the front end of shaft 46 for rotation therewith. On this shaft 54, the wire guide 28 is fixedly attached for rotation therewith.

The rotary drive of shaft 54 about its axis is effected by means of two toothed pulleys 56 and 58 which are interconnected by a toothed belt 60, whereby pulley 56 is attached nonrotatably to housing 50 by means of screws 62 and pulley 58 is fixedly attached to shaft 54 for rotation therewith. The winding wire is fed in through the hollow shaft 46 and opening 64 in bracket 52 via a roller 66 through hollow shaft 54 and via roller 38 to the outlet opening 36 of the wire guide 28. The coil feed is accomplished by axially shifting former 10 or 12 carried on an arm 67, for which purpose either arm 67 can be shifted along one or more guide bars 68 or arm 67 can be fixed to guide bars 68 and the latter shifted.

For selection of the transmission ratio between pulleys 56 and 58 and for determination of the rotary angular position, the same factors apply as stated above in connection with FIG. 6. An additional bearing bush 70 can be provided between gear 56 and shaft 46.

The embodiment according to FIG. 8 operates basically in the same manner as the embodiment of FIG. 7.

A shaft 78 mounted by means of bearing bushes 72 and 74 in a housing 76 is driven rotatably. It carries a bracket 80 firmly rotatably on its front end, in which a shaft 84 has been rotatably mounted in a bearing bush 82. A gear 86 is fixed to shaft 84 to rotate therewith, from which gear the wire guide 28 extends eccentrically of the axis of shaft 84. Upon rotation of shaft 78, gear 86 rolls around teeth of a ring gear 88 on housing 76, as a result of which shaft 84 is caused to rotate around its own axis. Again, the wire feed again takes place through hollow shafts 78 and 84, this time via a roller 90 mounted in said shaft 78. Bracket 80 is balanced by means of a counterweight 92.

As in the case of the embodiments given by way of example and described previously, the shape of the path of movemeht of wire guide 28 is governed by the ratio of the number of teeth of the ring gear 88 and of the gear 86. An ellipse will result in the case of a ratio of 2:1.

The coil feed is accomplished in essentially the manner as in the embodiment according to FIG. 7.

In the arrangement according to FIG. 9, a shaft is driven by means of a rotary drive, not shown, which shaft is mounted by means of bearing bushes 94 and 96 in a housing 98. On the front end of said shaft 100 and in a disc 102, a driver pin 104 is seated eccentrically, this pin engaging with an elongated hole 106 of a slide 108 carrying coil former 10 or 12. The slide 108 glides cyclically up and down, driven by the drive via pin 104, in a guide 110 of housing 98.

The rotary movement of shaft 100 is transmitted via toothed pulleys 40 and 42 and the toothed belt 44 stretched between said gears, to a shaft 116 mounted in housing 98 by means of bearing bushes 112 and 114. At the front end of shaft 116, the wire guide 28 is mounted firmly for rotation with shaft 116. The wire feed runs through shaft 116 and via a roller 118 mounted at its front end to the wire guide 28. Shaft 116 is shifted axially in bearing bushes I12, 114 and pulley 42 in order to accomplish the coil feed. Between pulley 42 and shaft 116 there is a spring-groove connection as described above with reference to FIG. 6.

In this embodiment, wire guide 28 can be guided only on an elliptical path and not also on for example a triangular or square path. The transmission ratio between pulleys 40 and 42 at the same time amounts to 1:1. The rotary angular position is adjusted in such a way that wire guide 28 will be in its uppermost position whenever slide 108 with former 110 is in its lowest position.

Sometimes it also is necessary to produce coils with two individual windings beside one another, whereby the connecting ends of the wire each time are to be on the outside. To produce such coils, the coil former shown in FIG. 10 will be used. It corresponds in principle precisely to the embodiment according to FIG. 6, with the difference that it includes two shafts 26a and 26b driven via the same toothed belt 44 and that the coil feed is accomplished not only by shaft 14 carrying former 10 or 12 but also by means of shafts 26a and 26b carrying wire guides 28. By means of wire guides 28, two coils are wound on two levels 122 and 124 on former 10 or 12 one beside the other by means of two separate winding wires simultaneously, but independently of one another. Shafts 26a and 26b in this case are moved oppositely in an axial direction, for which, in the case of the example, there is a two-armed lever 128 driven by a machine so it can be swung back and forth around a fixed rotational point 126. The lever 128 has a spoke encircling flange 130 on shaft 26a, and another yoke encircling flange l30b disposed at the rear end of shaft 26b.

Deviating from the details of FIG. 6, pulley 40 is seated firmly axially on shaft 14, while there is a springgroove connection permitting the axial shifting of the shafts 26a and 26b, between pulleys 42a and 42b.

Although the invention has been described in considerable detail with respect to preferred embodiments thereof, it will be apparent that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention.

l claim:

1 An apparatus for winding coils for electric machines and the like, wherein the coils have a polygonal cross-section, comprising:

a polygonal former, means for mounting the former to receive the windings of the coil thereon,

a wire guide, means for mounting the wire guide for delivering wire to the former,

said former mounting means and said wire guide mounting means together forming a further means for effecting a relative movement between the wire guide and the former according to which the relative path as between the'former and the wire guide is the composite of (a) a circular path encircling the former and (b) a further movement superimposed on the circular movement which causes the resultant path of the wire guide relative to the former to be flattened, relative to a true circle of the wire guide about the former, along at least the longest side of the polygon and which varies the velocity of the wire guide, relative to the former, along said resultant path, to reduce the acceleration of the increase in the unwinding speed of the wire from the wire guide immediately after the wire is laid onto said longest siderelative to what said acceleration would be for a truerelative circular path of the wire guide about the former.

2. An apparatus according to claim 1, wherein said further means includes means for decreasing the angular speed of the wire guide about the former, relative to what it would be in the case of a true circle about the former, at least in the said angular range where the wire is laid onto the said longest side.

3. An apparatus according to claim 2, wherein said further means includes means for causing said resultant path to be a continuously curved path in which certain portions of the path corresponding to at least some of the sides of the polygonal former are flattened, relative to a true circle about the former.

4. An apparatus according to claim 3, wherein the former is rectangular and the said curved path is an ellipse.

5. An apparatus according to claim 2 wherein said further means includes means for causing said resultant path to include some straight lined portions corresponding to at least some sides of the polygonal former.

6. An apparatus according to claim 5, wherein the former is a regular polygon and the said resultant path is a similar polygon but with the corners rounded.

7. An apparatus according to claim 6, wherein the further means includes means for causing said similar polygon to be turned angularly relative to the relative reciprocating movement between the former and the circular path of the wire guide perpendicular to the axis of the said circular path.

8. An apparatus according to claim 2, wherein said further means includes means for effecting relative reciprocating movement between the former and the circular path of the wire guide perpendicular to the axis of the said circular path.

9. An apparatus according to claim 8, wherein the last said means comprises a shaft mounted for rotation about an axis, said shaft including means mounted eccentrically of its axis connected to the former for reciprocating the former upon rotation of the shaft and transmission means connecting the said shaft to the wire guide to rotate the wire guide in cooperation with said reciprocating movement of the former. v

10. An apparatus according to claim 2, wherein said further means includes means for swiveling the former during movement of the wire guide through said circular path.

11. An apparatus according to claim 2, wherein said further means includes means for rotating the former about an axis passing through the center thereof while the wire guide is itself turning about a second axis spaced from the first axis.

12. An apparatus according to claim 1 1, wherein the last said means includes a shaft rotatable about the first axis, said former connected to the shaft for rotation therewith, a transmission connecting the shaft to a further shaft on which the wire guide is eccentrically mounted, whereby turning of the first shaft rotates both the former and the wire guide.

13. An apparatus according to claim 1 l,'wherein said former includes a plurality of levels adapted to be wound simultaneously, and including a pair of said wire guides, one for each of said levels and including a common means for rotating both wire guides andalso said former.

14. An apparatus according to claim 13, including means for moving the two wire guides parallel to their respective axes in opposite directions for effecting relative axial feeding motion between the wire guides and the former.

15. An apparatus according to claim 2, wherein said further means includes means for rotating the wire guide about a first axis, and rotating said first axis about a second axis which second axis passes through the central axis of the former, while the former is stationary against rotation about its said central axis, whereby the speed of rotation of the first axis is a whole number multiple of the speed of rotation about the second axis.

16. An apparatus according to claim 15, said further means including a housing, a shaft rotatable in said housing about said second axis, a toothed pulley fixed to the housing and encircling the said shaft, a bracket fixed to the first said shaft for rotation therewith and a further shaft freely rotatably mounted in said bracket and located on said first axis, the wire being eccentrically located on said further shaft, and a second toothed pulley fixedly connected to said further shaft, and a toothed belt interconnecting said toothed pulleys, whereby upon rotational movement of the first said shaft, the wire guide rotates about the said second axis as the wire guide turns about said first axis.

17. An apparatus according to claim 15, said further means including a shaft on said second axis, a bracket fixed to the shaft for rotation therewith and a further shaft freely rotatably mounted in the bracket on said first axis, a gear connected to said further shaft and said wire guide being fixedly connected to said gear eccentrically of said first axis and a ring gear co-axial with the second axis and surrounding and engaging said gear to effect said rotation about the first axis as the wire guide rotates about the second axis.

18. A method of winding a coil onto a polygonal former comprising:

mounting a polygonal former to receive a coil thereon,

directing wire to form the coil to a wire guide, and

effecting a relative movement between the wire guide and the former according to which the relative path as between the former and the wire guide is the composite of (a) a circular path encircling the former and (b) a further movement superimposed on the circular movement which causes the resultant path of the wire guide relative to the former to be flattened, relative to a true circle of the wire guide about the former, along at least the longest side of the polygon and which varies the velocity of the wire guide, relative to the former, along said resultant path, to reduce the acceleration of the increase in the winding speed of the wire from the wire guide immediately after the wire is laid onto said longest side relative to what said acceleration would be for a true relative circular path of the 10' wire guide about the former.

19. A method according to claim 18, including decreasing the angular speed of the wire guide about the former, relative to what it would be in the case of a true circle about the former, at least in the angular range where the wire is laid onto the said longest side.

20. A method according to claim 19, wherein the former is rectangular and the resultant path is an ellipse.

21. A method according to claim 19, wherein the former is a regular polygon and the resultant path is a similar polygon with rounded sides.

22. A method according to claim 21, wherein the said similar polygon is turned angularly with respect to the corresponding polygonal sides of the former such that wire is being unwound from the said rounded corners just as the wire is being laid onto a flat side of the polygonal former corresponding to the flat side of the similar polygonal path immediately before the said rounded corner. 

2. An apparatus according to claim 1, wherein said further means includes means for decreasing the angular speed of the wire guide about the former, relative to what it would be in the case of a true circle about the former, at least in the said angular range where the wire is laid onto the said longest side.
 3. An apparatus according to claim 2, wherein said further means includes means for causing said resultant path to be a continuously curved path in which certain portions of the path corresponding to at least some of the sides of the polygonal former are flattened, relative to a true circle about the former.
 4. An apparatus according to claim 3, wherein the former is rectangular and the said curved path is an ellipse.
 5. An apparatus according to claim 2 wherein said further means includes means for causing said resultant path to include some straight lined portions corresponding to at least some sides of the polygonal former.
 6. An apparatus according to claim 5, wherein the former is a regular polygon and the said resultant path is a similar polygon but with the corners rounded.
 7. An apparatus according to claim 6, wherein the further means includes means for causing said similar polygon to be turned angularly relative to the relative reciprocating movement between the former and the circular path of the wire guide perpendicular to the axis of the said circular path.
 8. An apparatus according to claim 2, wherein said further means includes means for effecting relative reciprocating movement between the former and the circular path of the wire guide perpendicular to the axis of the said circular path.
 9. An apparatus according to claim 8, wherein the last said means comprises a shaft mounted for rotation about an axis, said shaft including means mounted eccentrically of its axis connected to the former for reciprocating the former upon rotation of the shaft and transmission means connecting the said shaft to the wire guide to rotate the wire guide in cooperation with said reciprocating movement of the former.
 10. An apparatus according to claim 2, wherein said further means includes means for swiveling the former during movement of the wire guide through said circular path.
 11. An apparatus according to claim 2, wherein said further means includes means for rotating the former about an axis passing through the center thereof while the wire guide is itself turning about a second axis spaced from the first axis.
 12. An apparatus according to claim 11, wherein the last said means includes a shaft rotatable about the first axis, said former connected to the shaft for rotation therewith, a transmission connecting the shaft to a further shaft on which the wire guide is eccentrically mounted, whereby turning of the first shaft rotates both the former and the wire guide.
 13. An apparatus according to claim 11, wherein said former includes a plurality of levels adapted to be wound simultaneously, and including a pair of said wire guides, one for each of said levels and including a common means for rotating both wire guides and also said former.
 14. An apparatus according to claim 13, including means for moving the two wire guides parallel to their respective axes in opposite directions for effecting relative axial feeding motion between the wire guides and the former.
 15. An apparatus according to claim 2, wherein said further means includes means for rotating the wire guide about a first axis, and rotating said first axis about a second axis which second axis passes through the central axis of the former, while the former is stationary against rotation about its said central axis, whereby the speed of rotation of the first axis is a whole number multiple of the speed of rotation about the second axis.
 16. An apparatus according to claim 15, said further means including a housing, a shaft rotatable in said housing about said second axis, a toothed pulley fixed to the housing and encircling the said shaft, a bracket fixed to the first said shaft for rotation therewith and a further shaft freely rotatably mounted in said bracket and located on said first axis, the wire being eccentrically located on said further shaft, and a second toothed pulley fixedly connected to said further shaft, and a toothed belt interconnecting said toothed pulleys, whereby upon rotational movement of the first said shaft, the wire guide rotates about the said second axis as the wire guide turns about said first axis.
 17. An apparatus according to claim 15, said further means including a shaft on said second axis, a bracket fixed to the shaft for rotation therewith and a further shaft freely rotatably mounted in the bracket on said first axis, a gear connected to said further shaft and said wire guide being fixedly connected to said gear eccentrically of said first axis and a ring gear co-axial with the second axis and surrounding and engaging said gear to effect said rotation about the first axis as the wire guide rotAtes about the second axis.
 18. A method of winding a coil onto a polygonal former comprising: mounting a polygonal former to receive a coil thereon, directing wire to form the coil to a wire guide, and effecting a relative movement between the wire guide and the former according to which the relative path as between the former and the wire guide is the composite of (a) a circular path encircling the former and (b) a further movement superimposed on the circular movement which causes the resultant path of the wire guide relative to the former to be flattened, relative to a true circle of the wire guide about the former, along at least the longest side of the polygon and which varies the velocity of the wire guide, relative to the former, along said resultant path, to reduce the acceleration of the increase in the winding speed of the wire from the wire guide immediately after the wire is laid onto said longest side relative to what said acceleration would be for a true relative circular path of the wire guide about the former.
 19. A method according to claim 18, including decreasing the angular speed of the wire guide about the former, relative to what it would be in the case of a true circle about the former, at least in the angular range where the wire is laid onto the said longest side.
 20. A method according to claim 19, wherein the former is rectangular and the resultant path is an ellipse.
 21. A method according to claim 19, wherein the former is a regular polygon and the resultant path is a similar polygon with rounded sides.
 22. A method according to claim 21, wherein the said similar polygon is turned angularly with respect to the corresponding polygonal sides of the former such that wire is being unwound from the said rounded corners just as the wire is being laid onto a flat side of the polygonal former corresponding to the flat side of the similar polygonal path immediately before the said rounded corner. 